Field of the Invention
The present invention concerns a wheel construction for e.g. a construction or agricultural machine, such as a tractor, where the wheel construction at least includes a first wheel rim made up of a first rim ring for mounting a first tyre and further including a first hub plate with an outer periphery, the first hub plate at outer periphery being fixed to the rim ring at a distance X1 from an annular edge thereof, and extending internally in the first rim ring between the rim ring and the central axis of the first wheel rim (rotary axis of the wheel rim), the first hub plate at an inner periphery including a number of holes and a contact face for mechanical and detachable fixing to either a central hub plate or directly to a hub of a vehicle, wherein a possible central hub plate at an outer periphery includes a contact face and holes for direct or indirect joining with the first hub plate at its inner periphery, and at an inner periphery including a contact face and holes for joining with a hub on a vehicle.
Description of Related Art
The invention also relates to a method for manufacturing such a wheel construction.
It is commonly known that wheel rims suited for use on construction and agricultural machines are made of steel with a rim ring and a with a hub plate. Wheel constructions that include wheel rims with rim ring and hub plate in steel are used on many other types of vehicles. A typical design is that the rim ring is rolled in the wanted diameter and made with wheel rim edges and other geometric shapes such that a tyre can be fitted thereon. The hub plate typically consists of a steel plate that may be plane but which is typically shaped with one or more depressions—concave/convex. These depressions have partly the purpose of stiffening the hub plate and partly the purpose of offsetting the contact surfaces that are secured to a hub on a vehicle and to the inner side of the rim ring. On such a wheel rim is mounted a tyre suited for the specific purpose for which the machine in question is to be applied.
WO 2013/068018 A1 discloses a wheel rim and a method for making a wheel rim of the type suitable for use on an agricultural or construction vehicle, wherein the central hub plate at the outer periphery includes a number of tabs extending away from the centre of the central hub plate, where the second hub plate at its inner periphery also includes a number of tabs extending towards the centre of the hub plate, where the tabs have a geometric shape such that the tabs fit between each other, where the tabs include holes arranged at the same pitch circle diameter and at right angles to the tabs. In connection with the making of the hub plate, the second hub plate and the central hub plate can be produced from a single piece of suitable material, preferably steel plate, as the mentioned tabs extend over each other when two parts are separated and turned such that the tabs come to lie upon each other. The two hub plate parts are then joined by bolts in the holes formed in the mentioned tabs.
Over time, construction machines as well as agricultural machines have become larger and larger, and in order to minimise the impact of the weight of the machines on the base it is common to fit these machines with even very wide tyres, such as twin or terra tyres that can be e.g. 800, 900 or 1050 mm wide, or even wider. These types of tyres are wider than traditional tyres and thereby make less impact on the base, e.g. a field with crops, than a corresponding narrower standard tyre would do, thereby attaining a reduced field pressure. A reduced field pressure is precisely an important parameter in order to achieve an optimal production of crops since compressed soil does not produce a good yield.
In particular tractor tyres furthermore have a marked pattern on the tread of the tyre and typically include two rows, each with an amount of distinct oblique ribs, called pattern blocks that are pressed into the base, whereby the power from the tractor is transmitted to the base. On the very wide twin and terra tyres there may, however, be a drawback by these large pattern blocks since it is not always easy to ensure that the pattern blocks are pressed sufficiently into the base.
At the same time, by the wide tyres such as twin and terra tyres it is also necessary to regulate the air pressure in the tyres to a lower level when working in the field, whereas during transport on road, typically occurring with higher speed, there is a need for increased air pressure. The reason for this is that the best power transmission to the base is achieved by a low air pressure, why it used in the field, while the same low air pressure causes a very unstable and “floating” experience while driving on a solid base such as a tarmac road, and at higher speed. Traffic safety is therefore improved by increasing pressure in the tyres while driving on public roads.
The large and wide twin and terra tyres have been very expensive for a long time, and the cost has now increased even more, and unfortunately a corresponding longer service life of the tyres has not been achieved. In principle, the large twin and terra tyres are a necessary evil as the tyres are preferred in daily use, but price as well as wearability, and not the least the need of constant changing of the air pressure is a nuisance and a source to rising costs.